Partial overhaul of an Onan 2.8 generator

[rhythmtone]

Hi again,
I finally tore into this fully, I did de-mount the engine, because of the rust, and because I wanted to do it right.

But, as I figured might happen, I came across 2 questions - I found this great manual with parts numbers and diagrams to better explain myself:

https://drive.google.com/file/d/1agZ...w?usp=drivesdk

1. Do you have any parts numbers for the 4th mount, the one that's different from the others? Mine also didn't have it, but there is a mounting hole on the engine, so either they decided it wasn't necessary (for a different model, etc) or it fell off after years. To add to the confusion, I looked closely at the manual and didn't see it mentioned anywhere - maybe it's not necessary, maybe it would be a good thing to add? Either way, I'm a bit stumped on that.

2. Mine is a KV spec J - they have different pages trying to show the differences, etc. - but on page 36 (and others) it says that those long rubber mounts in your picture (x3) there are 2 different kinds of those as well - "yellow dot generator end" and "blue dot engine end" - I can just order the correct amount of each one and hope for the best, but I was wondering if you ran into this? They look very similar, but I did tear mine up because the bottom nuts were so rusty, it was going to be impossible to de-mount the engine and save those rubber mounts - and since you recommended replacing them, I just went for it.

Thanks again, I really appreciate any help with this,
Dave

[rhythmtone]

Actually nevermind the 1st question, I see it now, 402-0632 on page 39 - pricey! Haha

But question #2 still stands about the two different kinds of "long" rubber isolators that attach to the torx bolt assembly.

Thanks again,
Dave

[jmai]

From my research, the mount you mention is 402-0632

I ordered other three isolators just by the part numbers

2 of part # 402-0601-02
1 of part # 402-0601-01

I don't remember any real difference between the three parts-blue dot or yellow dot.

[rhythmtone]

Originally Posted by jmai

From my research, the mount you mention is 402-0632

I ordered other three isolators just by the part numbers

2 of part # 402-0601-02
1 of part # 402-0601-01

I don't remember any real difference between the three parts-blue dot or yellow dot.

Okay great, thanks for the reply, I appreciate it!

[nomadikus]

Originally Posted by jmai

If you want to test the generator once it is out of the RV, you will need to set it up. I placed my unit on a small moveable dolly with casters so it could easily be moved. I put the unit on blocks because it was not installed on the mounting base pan. If it doesn’t crank, check your grounds. The following connections need to be activated..

12V power from a battery- I removed the positive and negative cables from my RV and then used jumper cables. There should have been a positive cable that you previously disconnected. The negative jumper cable can be connected to a screw attached on the mounting base pan.

Is the screw attached on the mounting base pan on the left at the front of the channel that contains the fuel pump, relay, etc? I see a screw connected to the pan with several wires attached to it that I assume is the common ground? I tried just clipping my alligator clip to the frame and the gennie doesn't seem to want to turn over at all. This is in contrast to when I had it hooked up to my RV where it was starting like a champ (after a carb replacement).

[jmai]

Here are some details about the ground cables.

Generator connections when the unit is removed

If you want to test the generator once it is out of the RV, you will need to set it up. I placed my unit on a small moveable dolly with casters so it could easily be moved. I put the unit on blocks because it was not installed on the mounting base pan. If it doesn’t crank, check your

Ground wires-If your unit is still not attached to the mounting base pan, you will need to connect several ground cables from some of the components. It should be noted that you need to have excellent contact between the ground wires and the engine and mounting base pan. Clean the wire end terminals and use new star washers. I use a multi-meter to check connections as I assemble the components. I also used an anti-corrosive spray or just coat the connections with a dielectric grease or silicone paste. This will help to prevent corrosion. These are the grounds connections.

1. Four wires from the wiring harness (left front next to the end plate). These
wires attach to a stud attached to the bottom of the mounting pan base.
2. Coil (a small blue box with a small black wire)
3. Engine block
4. Fuel pump.

I used some wire and alligator clips for a temporary set-up.

120V outlet-I just connected these wires (white, black and green) to a standard receptacle in an electrical box. This will be used to connect the load and to measure the frequency (Hz) and voltage

[nomadikus]

Okay, just in case anyone comes across this thread in the future, I was insufficiently grounded. As soon as I resolved this problem it started to turn over as aggressively as expected. The grounds are quoted below - knowing we're talking something like 400 amps to crank, I wanted a big enough 'pipe' for the current to flow so I attached my black clip to a piece of metal on the engine body. I've attached a photo with a good connection point highlighted (as well as the 12v hot cable input in case anyone is not familiar).

Note that the bottom case is actually common ground but the paint on it is an electrical insulator so you have to find a good chunk of unpainted + exposed metal for your clip (like what I've shown in the image).

Originally Posted by jmai

1. Four wires from the wiring harness (left front next to the end plate). These
wires attach to a stud attached to the bottom of the mounting pan base.
2. Coil (a small blue box with a small black wire)
3. Engine block
4. Fuel pump.

[nomadikus]

In the interests of completeness, just because piecing together Onan 2800 fixes from youtube and forums has been pretty hit and miss for me, I want to report that disconnecting S2 does not seem to have fixed my problem! I'm not certain what to try next but I guess I'll hit the troubleshooting guides and try to figure out which cutoffs are disabled while the start button is depressed. It certainly seems like one of them may be killing things.

Here's a short video (mp4) of my setup, using a lithium jumper to start things, fuses seem fine, S2 disconnected, starts right up (once I reconnected the choke) and seems to run great but then dies immediately once I'm no longer pressing start. Maybe someone can help me diagnose from the audio!

https://drive.google.com/file/d/17GN...ew?usp=sharing

[eric1514]

Originally Posted by nomadikus

In the interests of completeness, just because piecing together Onan 2800 fixes from youtube and forums has been pretty hit and miss for me, I want to report that disconnecting S2 does not seem to have fixed my problem! I'm not certain what to try next but I guess I'll hit the troubleshooting guides and try to figure out which cutoffs are disabled while the start button is depressed. It certainly seems like one of them may be killing things.

Here's a short video (mp4) of my setup, using a lithium jumper to start things, fuses seem fine, S2 disconnected, starts right up (once I reconnected the choke) and seems to run great but then dies immediately once I'm no longer pressing start. Maybe someone can help me diagnose from the audio!

https://drive.google.com/file/d/17GN...ew?usp=sharing

I apologize. I haven't read this whole thread, but can you try bypassing the starter switch, you know, hot wire it? That switch is also how you turn the thing off and perhaps it's faulty.

[nomadikus]

My switch is working fine. I've somehow developed fresh new problems - my starter is spinning, the fan assembly is spinning, I see a small voltage developing on the output lines and I'm getting spark but there is no attempt to turn over. I'm going to have to check fuel again I guess, see if my pump went bad during this whole operation.

Originally Posted by eric1514

I apologize. I haven't read this whole thread, but can you try bypassing the starter switch, you know, hot wire it? That switch is also how you turn the thing off and perhaps it's faulty.